Electric furnace



Dec. 17, 1935.

J. C. WOODSON ELECTRIC FURNAGE Patented Dec. 17, 1935 UNITED STATES PATENT OFFICE ELECTRIC FURNACE Pennsylvania Application January 23, 1934, Serial No. 707,910

8 Claims.

My invention relates to electric furnaces, and it has particular relation to improvements in the structural design of galvanizing and other 'equivalent furnaces, in which heating elements are positioned intermediate the walls of an outer refractory Chamber and a Crucible container supported therein, and to the provision of leak-indicating means for metal-melting furnaces of this type.

In all past constructions of furnaces of this type with which I am familiar, it has been necessary to remove the Crucible in order to effect a replacement of a heating element, such replacement being necessary in the event of damage or failure which frequently occurs during normal operation of the furnace. It has thus been necessary to not only cool the charge but also to lift the heavy crucb'le and its contents bodily out of the refractory chamber before access can be gained to the heater elements. As a consequence such replacement operations have, in the past, been exceedingly expensive, diicult of accomplishment and wasteful of time.

In galvanizing and other operations in which corrosive metal is involved, leaks sooner or later are likely to develop in the containing Crucible. The molten metal which thus drains into the refractory chamber may, if allowed to there solidify in any considerable quantity, seriously damage the brick work and heating elements. If an operator be advised immediately when a leak occurs he may, however, .prevent such damage by ladling out the molten metal and removing the defective Crucible.

My invention is directed to an improved Construction and arrangement of parts for furnaces of the type under consideration which overcomes the element-replacement disadvantages named, and which additionally contemplates the provision of a signal system for advising an operator of an escape of molten metal from the Crucible.

Generally stated, an object of my invention is to provide an improved construction for furnaces of the above described type which permits of access to the heating elements without removing or even disturbing the normal position of the crucible container between which and the outer refractory wall the heating elements are located.

A more specific object of my invention is to provide an improved furnace construction of the type indicated in which the removal of a wall cover plate and the removal of a single layer of brick positioned thereunder allows the damaged section of heating element to be directly lifted out vertically and a repair element put in its place.

Another object of my invention is to provide a leak indicating system for metal-melting furnaces which will immediately warn an operator of the presence of molten metal in the refractory or heating element chamber.

Additional objects and advantages of my invention will best be understood through a description of a specific embodiment thereof when taken in conjunction with the accompanying drawings in which:

Figure 1 is a View in lengthwise vertical section of an electric furnace embodying the improved construction of my invention;

Fig. 2 is an end view of the furnace of Fig. 1, partially in section and partially in elevation, showing further details of one preferred manner of heater element suspension and the establishment of connections therewith to terminals which extend to the outside of the furnace Wall, and

Fig. 3 is a top or plan view of one end of the furnace of Figs. 1 and 2 which shows the arrangement of the detachable wall cover plates and the layer of removable bricks, a portion of the Crucible Cover being cut away to more clearly illustrate this construction.

Referring to the drawings, the furnace there illustrated is of a Well known galvanizing-pot or other equivalent type which comprises enclosing walls of heat refractory material t0, which, together with a bottom member of the same material, form an open-top chamber. Positioned in this chamber is a crucible l2 for containing the material to be treated, which Crucible is supported, in the structure shown, from the base of the furnace by members I4 upon which it directly rests. A sheet metal shell I6 completely covering the outer portions of the refractory walls l!) effects the necessary structural reinforcement thereof. The furnace is provided with the usual cover I8 which is attached thereto by means of hinge members 2) arranged to permit opening. In the drawings this cover is shown in the closed position.

For the purpose of heating the furnace, a plurality of electrical resistance elements 24 are positioned between the refractory walls l0 and the Crucible l2. Preferably these elements are of the unit type, one preferred construction for which is covered by United States Patent No. 1,695,882, which issued December 18, 1928, to O. A. Colby. It will be understood, however, that insofar as the improved construction of my invention is concerned, heating elements of other designs may be used with equal success.

As shown, each heating element comprises a plurality of horizontal loops of conductor 26 held in position by assemblages of vertically disposed insulating blocks 28 that are mounted upon a rod or bolt 30 and secured thereby to a member 32 by means of which they are supported from the furnace Walls. Connections from a suitable source of power (not shown) are established with the ends 34 of the conductor of each heater element by means of terminals 36 which extend to the outside of the furnace structure.

Heretofore, as already pointed out, in furnaces of this and other equivalent types it has been necessary to lift the crucible I2 from the refractory chamber in order to effect a removal and replacement of any of the heater elements 24'. The construction of the present invention eliminates this disadvantageous requirement through the provision of means for removably hanging each of the several heater elements from the associated refractory wall over the top edge of which the terminals 35 are brought out. By removal of a wall cover plate d@ and the lifting out of the bricks 42 which are positioned above the heater element 24 which it is desired to replace, the complete element assemblage including the terminal connections can be lifted out vertically and another one installed in its place while the crucible is in its normal position. In fact, as already indicated, this replacement can, if necessary, be made while the furnace is still hot.

In order to facilitate the removal of the Wall cover plate 4B, it is divided, as is indicated in Fig. 3, into a plurality of separate sections each of which is secured in position by means of bolts 44 which, upon removal, free the section for witha drawal. In the drawings each section is shown as extending from they center line of the furnace drawn inthe direction of its width around the corner thereof to the center line of the structure drawn in the direction of its length. Thus in Fig. 3, in which gure is shown one of the cover plates removed to better illustrate the arrangement of the bricks 62 therebeneath, the removed plate covers the top of the end wall shown in the loWer half of the figure and the top of the side wall, also shown in the lower half of the figure, which extends from the middle of the furnace to the right hand end.

Itv will beapparent that other sub-divisions of the wall cover plate can be made, the only requirement being that the sections can readily be withdrawn to expose the removable bricks 42.

As is also best illustrated by the showing of the lower right hand corner of Fig. 3, the bricks 42 are preferably each so dimensioned as to cover a space corresponding to the position of one of the heater element supporting members 32 located therebeneath. If desired, however, bricks of other dimensions may be used as long as they are so tted that they may be readily lifted out after the wall cover plate 4) has been removed. In the showing of Fig. 3 one of the bricks which occupies the position over the end of the heater element 2t and the associated terminal connection 36 (these parts being shown in full lines at the lower portion of the ligure) ,-has been removed to allow a more clear illustration. of details.

It will be observed that the end of each of the heater element supports 32 is provided with a downwardlyextending projection which fits into a similarly shaped recess in the top of the wall I0 from which the heater element is supported. The

weight of the heater element may thus be carried by the horizontal portion of the support 32 resting on top of the Wall IIJ, while the projection holds the element in the desired position close to the wall side. 5

Each of the ends 34 of the heater element conductor is brought out in the manner shown over the top edge of the wall I and is joined in any suitable manner such as brazing, clamping, or through a screw-thread connection, with the body portion of the terminal 36.V In the top of the wall I0 a suitable groove 5B is preferably made to accommodate the terminal and the conductor with which it is joined. A slot 52 (Fig. 2) is cut in the sheet I6 comprised by the outer metallic shell surrounding the furnace, to allow the terminal 36 which extends through the wall to be lifted vertically out of the furnace, while a block of insulating material 56 provided with a closer fitting or narrower slot, is attached to the Wall to position the terminal 36 and prevent it from making Contact with the metal I6.

With this particular construction and arrangement of parts it will thus be apparent that to remove any one of the heater elements 24 from the furnace structure, it is only necessary to take out the bolts 44, which hold the associated section of the wall cover plate 4G in place', remove this section of cover plate, lift out the bricks 42 which are positioned over the heater element, and then vertically lift the element and the associated terminals 36 vertically out of the furnace. This having been done, another or replacement element may be inserted into the vacant position, the bricks i2 replaced, and the section of the cover plate it returned to, and attached in, its normal position.

In an actual installation of an electric furnace construction in accordance with the teachings of my invention, it will be understood that in establishing connections from the heater element terminals to the power source there may be provided a common terminal board from which suitable conductors are run to each of the individual elements. of installation forms no part of the present invention, no attempt to show it has herein been made.

The improvement in mechanical design of the furnace having been described, attention may 50 now be directed to the leak-indicating means of my invention. The bottom of the furnace heating chamber of refractory material lil is so shaped or sloped as to direct any molten metal which fallsV thereon from a. leak in the Crucible 55 i2 toward one of several outlet conduits 6G (best shown in Fig. 2) through which the metal may escape to the outside of the furnace. In front of the inner end of each of these conduits is formed, in the heating chamber bottom, a de- 60 pression 32 in which .depression are supported the ends 54 of two separated conductors 86 which are connected with terminals @8 suitably positioned on the outside of the furnace structure.

Connected With each of these several sets of 65 terminals t8 is an alarm circuit l which serves to control the operation of one or more signalling devices, shown in the drawings in the form of a bell 'i2 and a'lamp 74 associated with a battery or other energizing source le. It will be understood that these devices may be placed in locations most appropriate for attracting the attention of the furnace operator, andV that if desired they may be supplemented by additional alarm means (not shown).

Inasmuch as this particular-feature 4'5/ In operation of the leak-indicating system, the formation of a leak in the crucible I2 allows molten metal to flow into and i'lll one of the depressions 62. This metal completes a connection between the conductor ends 64 and thereby establishes an energizing circuit for the alarm devices 12 and 14, which circuit may be traced in Fig. l, from the upper terminal of battery 16, through the upper Conductor 10, the lower terminal 68, one of the conductors 66, the conductor ends G4 joined by the molten metal, the other conductor 66, the upper terminal 68, the second conductor 16, and the .devices 13 and 14 back to the lower terminal of battery 16.

Thus energized these devices immediately Warn the operator of the leaky Crucible and enable him to take proper steps to prevent damage to the furnace, as for example to ladle out the molten metal and remove the defective vessel before the brick work or heating elements have been appreciably injured.

Although I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention, therefore, is not to be restricted except insofar -as is necessitated by the prior art and by the scope of the appended claims.

I claim as my invention:

1. In an electric furnace comprising an opentop chamber formed by a heat-refractory wall, a crucible for containing material to be treated, positioned inside of said chamber, and a heating element positioned intermediate the Crucible and the chamber wall, the combination of means for so supporting said element that it may be re moved for replacement while the crucible remains in its normal position, said means comprising supports for removably hanging the heating `element from the chamber wall, terminal connections brought out over the top edge of said wall, and removable covering means for the wall top and the heating element.

2. In an electric furnace comprising refractory walls forming an open-top chamber, a Crucible supported inside of said chamber, and a plurality of heating elements positioned around the interior of the chamber intermediate the Crucible and the said walls, the construction in which each of said heating elements may be individually removed and replaced without disturbing the normal position of the crucible or that of the remaining heating elements, said construction comprising means for removably supporting each heating element from one of the chamber walls, means for bringing over the top edge of the wall to the outside of the furnace terminals connected with the element, and means for covering the top of the wall and the heater element with refractory material adapted to be readily removed.

3. An electric furnace comprising, in combination, an outer wall forming an open-top chamber, a crucible positioned therein, heating elements disposed between the Crucible and the wall, means for removably supporting each element from the wall structure, and means for bringing over the top of said wall to the outside of the furnace connections from each element in such manner that the element and associated Connections may be lifted vertically out of the furnace.

4. An electric furnace comprising, in combination, an outer Wall forming an open-top chamber,

a Crucible positioned therein, heating elements disposed between the Crucible and the wall, means for removably supporting each element from the wall structure, and means for bringing over the top of said wall to the outside of the furnace connections from each element in such manner that the element and associated Connections may be lifted vertically out of the furnace, said last-named means comprising terminals which extend beyond the outer edge of the furnace walls, and supporting means for the terminals which allow withdrawal in the vertical direction.

5. An electric furnace comprising, in combination, an outer wall forming an open-top chamber, a Crucible positioned therein, heating elements disposed between the crucible and the wall, means for removably supporting each element from the wall structure, means for bringing to the outside of the furnace Connections from each element in such manner that the entire element assemblage may be lifted vertically out of the furnace, and refractory covering material for the top of the walls in the form of a layer of bricks, removably laid thereon.

6. In an electric furnace comprising a refractory-material wall forming an open-top chamber, a Crucible positioned therein, a sheet-metal Casing positioned on the outside of said wall, and heating elements removably supported between the crucible and the wall in such manner that they may be lifted vertically therefrom, the combination of refractory covering material for the wall top in the form of a layer of bricks removably laid thereon, and a top cover plate for ,said bricks comprising a metal sheet removably secured to the top edge of the sheet metal casing of the furnace.

7. In an electric furnace comprising a wall of refractory-material forming an open-top chamber, a Crucible positioned therein, a sheet-metal casing surrounding the outside of said Wall, heating elements removably supported between the Crucible and the wall, and means, including terminals, for bringing Connections from each element over the top of said wall to the outside of the furnace in such manner that the element assemblage may be vertically lifted therefrom, the combination for each terminal of a vertical slot Cut in the top edge of the sheet-metal casing, in which slot the terminal reposes and out of which it may be vertically lifted, and a block of insulating material provided with a narrower and shorter slot so attached to the metal sheet as to position the terminal out of Contact with the sides of the slot therein.

8. In combination with a furnace comprising side and bottom walls arranged to form a heating chamber, a Crucible for holding molten metal positioned inside of said chamber, and outlet passageways arranged in metal receiving posi tions below said Crucible, a leak-indicating system comprising an alarm device, and means responsive to metal escaping through said outlet passageway for Controlling said alarm device, said means comprising an energizing circuit for said alarm device, said circuit including a pair of separated conducting bodies positioned at the entrance of each passageway in a manner tov be bridged by the escaping metal.

JAMES C. WOODSON. 

